Introduction+to+8085

8/3/2019 Introduction+to+8085

http://slidepdf.com/reader/full/introductionto8085 1/24



` The microprocessor is one of the most important

components of a digital computer.

` It acts as the brain of the computer system.

` As technology has progressed, microprocessorshave become faster, smaller and capable of doing

more work per clock cycle.

` Sometimes, microprocessor is written as µP .

( µ is pronounced asMu

)



` Definition:

Microprocessor is the controlling unit or CPU of a micro-

computer, fabricated on a very small chip capable of

performing ALU operations and communicating with theexternal devices connected to it.



` A computer: Accepts the data from the user.

Stores the data and the set of instructions supplied by the

user in memory.

Processes the data according to the instructions in theprocessing unit.

Communicates the result to the user or stores it for

further reference.



` A computer has the following units: Input Unit

Output Unit

Memory Unit

Central Processing Unit



` INPUT UNIT The input unit consists of the devices which accept the

data and instructions from the user and communicates it

to the CPU.

The various input devices are: keyboard, mouse, joystick,trackball etc.

` OUTPUT UNIT

It provides the result of the various operations performedby the CPU to the user.

The various output devices are: printers, monitors,

loudspeakers etc.



` CENTRAL PROCESSING UNIT (CPU) The CPU is the heart and nerve centre of the computer.

It fetches the instruction and data from the peripheraldevices and performs all the arithmetic operations, takes

logical decision and control the operation of all other units.

Various sub-blocks of the central processing unit are:

x Arithmetic and Logic Unit (ALU)

x Timing & Control Unit

x Registers



` ARITHMETIC AND LOGIC UNIT (ALU) This unit perform all the logical and arithmetic operations. Various arithmetic operations are: addition, subtraction, increment

and decrement etc. Various logical operations are: AND, OR, NOT, XOR, etc.

` TIMING AND CONTROL UNIT This unit controls the entire operations being performed by the

system. It controls the operations of ALU, input/output devices and

memory unit. This unit interprets the instructions and generates various timing

and control signals.` REGISTERS

A register is a very small amount of very fast memory that is builtinto the CPU in order to store the current data and instructionswhich are being executed by the CPU.



` MEMORY UNIT It stores the program statement and the data i.e. the

information supplied from the input unit.

It also stores the final output.

This is connected to the CPU by means of a bidirectionalbus.

The CPU processes the information as taken from the

memory and performs the operations in the ALU section.

The results are either transferred to the output unit or

stored in the memory for later use by the CPU.



` As the name implies, microcomputers are small

computers.

` The block diagram of the microcomputer is similar to the

computer except that the central processing unit of the

microcomputer is contained in a single IC called themicroprocessor.



` A microprocessor is a LSI (Large Scale Integration) ICthat does almost all the functions of the CPU.

` It is also defined as a CPU contained in a single chip.` The basic function of the microprocessor is:

to fetch the instructions stored in the main memory identify the operations and the devices involved in it and accordingly generate control signals to determine when a

given action is to take place.

` We can say that a computer with a microprocessor asits CPU, is known as Microcomputer .



` Microprocessor: The central processing unit built on a single IC is called

Microprocessor.

A microprocessor (sometimes abbreviated as µP) is a

digital electronic component with miniaturized transistorson a single semiconductor integrated circuit (IC).

One or more microprocessors typically serve as a central

processing unit (CPU) in a computer system or handheld

device.



` Microcomputer: A digital computer, in which one microprocessor has

been provided to act as a CPU, is called Microcomputer.

A desktop computer, laptop, notebook, palmtop, etc.

contain one microprocessor to act as a CPU and hencethey come under the category of microcomputer.

The term microcomputer is generally synonymous with

personal computer.



` Multiprocessor System: The CPU of a large powerful digital computer contains

more than one microprocessor.

High-end powerful servers, mainframe computers,

supercomputers, etc. contain more than onemicroprocessor to act as CPU.

A computer whose CPU contains more than one

microprocessor is called Multiprocessor System.



` Microcontroller: A highly integrated chip that contains all the components

such as CPU, RAM, some form of ROM, I/O ports, and

timers is called Microcontroller.

Unlike a general-purpose computer, which also includesall of these components, a microcontroller is designed for

a very specific task to control a particular system.



` Instruction Set: The set of instructions that a microprocessor can

understand.

` Bandwidth: The number of bits processed in a single instruction.

` Capability: It depends upon the number of instructions and capability

of each instruction.



` Clock Speed: The clock speed determines how many operations per second

the processor can perform.

It is also called Clock Rate.

Every computer contains an internal clock that regulates therate at which instructions are executed and synchronizes thevarious computer components.

The faster the clock, the more instructions the CPU canexecute per second.

Clock speeds are expressed in megahertz (MHz) or gigahertz

(GHz). The microprocessors of personal computers have clock

speeds of anywhere from 300 MHz to over 3.8 GHz.



` Word Length: It depends upon the width of internal data bus, registers,

ALU etc.

An 8-bit microprocessor can process 8 bit data at a time.

A processor with longer word length is more powerful andcan process data at a faster speed as compared to

processor with shorter word length.

The word length ranges from 4 bits for small

microprocessor, to 64 bits for high-end microcomputers.



` Width of Data Bus: This is the size of the data bus. It defines the number of bits

that can be transferred through data bus.

` Width of Address Bus: This parameter decides the memory addressing capability of

the microprocessor. The maximum size of the memory unit isdecided by this parameter.

` Input/Output Addressing Capability: The maximum number of the input/output ports accessed by

the microprocessor depends upon the width of the input/outputaddress provided in the input/output instruction.



` Data Types: The microprocessor handles various types of data

formats like binary, BCD, ASCII, signed and unsigned

numbers.

` Interrupt Capability: Interrupts are used to handle unpredictable and random

events in the microcomputer.

It is used to interrupt the microprocessor. Interrupt driven input/output improves the throughput of a

system.



` Cost: The most important feature of a microcomputer is its low cost. Because of the widespread use of microprocessors, the volume of

production is very high. That is why, microprocessor chips are available at fairly low

prices.

` Size: The second important feature of a microprocessor is its small

size. As a result of improvement in fabrication technology, VLSI,

electronic circuitry has become so dense that a minute siliconchip can contain hundred and thousands of transistors.



` Power Consumption: Another important feature is its low power consumption. Microprocessors are normally manufactured by Metal-Oxide

semiconductor technology, which has the feature of low power consumption.

` Vers

atility:

The microprocessors are versatile. Keeping the same basic hardware, a microprocessor-based

system can be configured for a number of applications by simplyaltering the software program.

` Reliability:

Another important property of microprocessors is its extremereliability. It has been established that the failure rate of an IC is fairly

uniform at the package level, regardless of its complexity.



` A unit of length equal to one millionth of a meter.

` It is denoted by µ (Mu).

` For Example:

If we pluck a hair from the head, it is very thin. But a hair is more than 2000 times wider than a transistor

on a microprocessor.

Wires between transistors are even thinner.

They're more than 4000 times thinner than a hair.

A hair is about 100 microns in diameter.

That means, a transistor is just 0.045 microns wide.



Introduction+to+8085

Documents